Search UAPKI public key on CMP server.

SearchCmp.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Http;
using System.Threading.Tasks;

namespace CA_Client.Helpers
{
    internal static class SearchByCmp
    {
        private static int GetHexVal(char hex)
        {
            int val = (int)hex;
            //For uppercase A-F letters:
            //return val - (val < 58 ? 48 : 55);
            //For lowercase a-f letters:
            //return val - (val < 58 ? 48 : 87);
            //Or the two combined, but a bit slower:
            return val - (val < 58 ? 48 : (val < 97 ? 55 : 87));
        }

        private static byte[] HexToBytes(string hex)
        {
            if (hex.Length % 2 == 1)
                throw new ArgumentException("The hexadecimal key must have an even number of digits");

            byte[] arr = new byte[hex.Length >> 1];

            for (int i = 0; i < hex.Length >> 1; ++i)
            {
                arr[i] = (byte)((GetHexVal(hex[i << 1]) << 4) + (GetHexVal(hex[(i << 1) + 1])));
            }

            return arr;
        }

         public static byte[] GetCertBundle(string url, string keyId1, string keyId2)
        {
            string pre = "30818706092a864886f70d010701a07a04780d0000000000000002000000";
            string post = "0000000000000000000000000000000000000000000000000000000000000000010000000100000000000000";

            if (keyId1.Length == 40)
                keyId1 += "000000000000000000000000";
            if (keyId2.Length == 40)
                keyId2 += "000000000000000000000000";

            if ((keyId1.Length != 64) || (keyId2.Length != 64)) 
                throw new ArgumentException("CMP supports only DSTU keys");

            var req = HexToBytes(pre + keyId1 + keyId2 + post);
            var byteContent = new ByteArrayContent(req);
            var client = new HttpClient();
            var result = client.PostAsync(url, byteContent).Result.Content.ReadAsByteArrayAsync().Result;
            if (result.Length < 280)
                throw new Exception("Certificates not found");

            if (result.Length > 65536)
                throw new Exception("Response too long");

            int offset = 31;
            var bundle = new byte[result.Length - offset];
            Array.Copy(result, offset, bundle, 0, result.Length - offset);
            return bundle;
        }
    }
}